Infrared spectroscopy was used to determine fictive temperature of silica glasses. Positions of both the fundamental structural band at ∼ 1122 cm - 1 monitored in infrared (IR) reflection mode and an overtone of this band at ∼ 2260 cm - 1 monitored in IR transmission mode were found to be directly correlated with the glass fictive temperature. At any particular fictive temperature, the equilibrium structural band positions were found to be independent of the impurity content, such as hydroxyl, in different types of silica glass. From band shifts, the average Si O Si bond angle was computed to decrease by about 1.3° when the fictive temperature increased from 950 to 1400°C. Using this method, fictive temperatures of various as-received silica glasses were determined.